The present invention relates to a belt roller having a wind-up spring disposed between a housing part and a shaft onto which the belt is wound, the wind-up spring effecting wind-up rotation of the shaft, and a comfort spring serially actuatable in connection with the wind-up spring via a ratchet gear and exerting a lesser spring force than the wind-up spring. The inner end of the comfort spring is secured to the shaft and the outer end of the comfort spring is secured to the ratchet gear. The inner end of the wind-up spring is secured to the ratchet gear and the outer end of the wind-up spring is secured to a housing part. A blocking link is provided for controlling the springs which is moveable into engagement with the ratchet gear and is selectively moveable into or out of engagement with the ratchet gear by operation of a switch element which effects the switching over between the springs. The switch element is comprised of a reduction drive having several toothed gears which mesh with one another and which is operable to displace a switch lever that controls the blocking link. The switch element, as a function of the number of rotations of the shaft following the beginning of the uncoiling of the belt, switches off the wind-up spring as it switches to the comfort spring and, during winding-up of the belt, the switch element switches back to the wind-up spring after a predetermined number of rotations of the shaft.
A belt roller with the above described features is disclosed in EP 0 568 820 A1; to the extent that two serially actuated springs of differing spring force are provided in known belt rollers, the belt retraction force which is exerted during the deployed condition of the belt when the belt is disposed across the shoulder of the seat inhabitant should be reduced due to the diminished dimensions of the comfort spring while the full force of the wind-up spring should be effective during wind-up of the belt after it has been unbuckled. The respective switching of the two springs is effected via a ratchet gear actuated in connection with such switching; the ratchet gear, during its blocking by means of a blocking link controlled by a switch element, operates such that only the comfort spring operates on the shaft during the blocking. In the state of the art representative belt roller described in EP 0 568 820 A1, the switch element is configured as a toothed gear device having three outer toothed gears meshable with one another; furthermore, there are engageable with the blocking lever driven by the toothed gear device, which comprises a portion of the switch element, an additional control gear, a pivotable follower gear, and a pull lever coupled with the additional control gear whose impact limits and controls the movement of the blocking link. Since additional springs are provided for the coupling of the components of the switch element, there is produced a complicated configuration of the switch element with numerous individual pieces whose assembly and adjustment for a correct usage is expensive.
The invention addresses the challenge of providing a belt roller having the appropriate components which simplify the configuration of the switch element for the switching to the respective spring and which assure the reliability of its operation such that, even in the event of unfavorable manufacturing tolerances and friction losses, the strength of the comfort spring is sufficient to ensure a switching back to the wind-up spring.
The solution to this challenge is shown in the advantageous embodiments and variations recited in the claims hereto which follow the descriptions of these embodiments and variations.
The invention provides a basic solution in which the portion of the reduction drive which engages the switch lever is configured as a follower gear for directly contacting the switch lever which extends along a peripheral region and which has a notch for engaging the switch lever, and in which the reduction relationship of the reduction drive is arranged such that the rotation of the shaft, which begins with the uncoiling of the belt and continues until reaching the switch point for switching from the wind-up roller as defined by the extension of the notch, is less than a full rotation of the follower gear, and, further, in which the range of the belt uncoiling, which is accomplished against the bias of the wind-up spring, is determined by the extension of the notch which maintains the blocking pawl out of engagement with the ratchet gear by means of the predetermined position of the switch lever. The advantage is tied in with the invention that, because of the preset large reduction relationship of the reduction drive of, for example, 40:1, the force needed from the relatively weaker comfort spring to effect a take-up of the belt is kept low; at the same time, the setting of the switchover time point effectuated by the notch which engages the switch lever is easy to configure and to operationally preset. In this regard, the invention comprises features that permit a definite switchover time point for switching to the comfort spring to be specified.
In accordance with one embodiment of the invention, it is provided that the outer teeth of the ratchet gear are configured and arranged such that, outside of the extension of the notch and the engagement of the blocking pawl during belt uncoiling, the blocking pawl slides over the outer teeth of the ratchet gear and then only engages the ratchet gear for switching to the comfort gear upon re-coiling or taking up of the belt in the wind-up direction.
It thus occurs that the further uncoiling of the belt, which follows an overrunning of the switchover time point that is specified by the configuration of the extension of the notch, must be performed against the bias of the wind-up spring because the blocking pawl slides away along the correspondingly configured outer teeth of the ratchet gear such that a fixation of the ratchet gear does not occur during this uncoiling of the belt. The outer teeth of the ratchet gear engage the blocking pawl, which has been pivotally biased against the periphery of the ratchet gear, only upon the beginning of a take-up or wind-up of the belt and the fixation of the ratchet gear at that time effects then a switching over to the comfort spring.
In accordance with an embodiment of the invention, a tensioning spring is provided for biasing the switch lever into its disposition in which it effects a switching over from the wind-up spring; the arrangement of this tensioning spring does not require any particular fine adjustment as the tensioning spring is kept out of its biasing function by means of the direct engagement of the notch with the wind-up spring which occurs during the belt uncoiling range as effectuated by the operation of the wind-up spring.
In accordance with an embodiment of the invention, the blocking pawl is biased by means of a spring toward the direction for engaging the outer teeth of the ratchet gear, and the spring that biases the switch lever is configured with a greater spring force than the spring that biases the blocking pawl.
Additionally, a pull lever can be provided which frictionally follows the shaft as it rotates during belt uncoiling and which maintains the blocking pawl out of engagement with the ratchet gear during the activated regime of the wind-up spring; in this manner, an advantageous noise reduction during the rotation of the shaft including the ratchet gear is ensured throughout those portions of the belt wind-up range or, respectively, the belt uncoiling range during which the wind-up spring is performing its biasing activity.